Try OpenEdge Now
skip to main content
Database Administration
Reference : Virtual System Tables : Virtual system table summaries : Buffer activity (_ActBuffer)
 
Buffer activity (_ActBuffer)
The _ActBuffer VST displays the activity of the database buffer cache, such as the number of logical reads and writes, OS reads and writes, checkpoints, deferred writes, LRU skips and writes, and APW enqueues.1
Note: The _ActBuffer table, which contains buffer activity data, holds three records: the first record contains the totals of both the Alternate and primary buffer pools; the second record contains data on the primary buffer pool; the third record contains data on the Alternate Buffer Pool
Field name
Data type
Description
_Buffer-Active
INT64
Number of buffers active in each buffer pool
_Buffer-APWEnq
INT64
Number of modified buffers placed on the APW queue for writing.
_Buffer-Area
INT64
Area number
_Buffer-BlockMap
INT64
Block allocation bit map block (Contains a bit map of block allocation within the object. It is allocated, but is currently not used. Accesses can show up in the buffer pool.)
_Buffer-Chkpts
INT64
Number of checkpoint operations.
_Buffer-ClusterMap
INT64
Cluster bit Map Blocks (Contains a bit map of cluster allocation within the area. It is allocated, but is currently not used. Accesses can show up in the buffer pool.)
_Buffer-Control
INT64
Number of control blocks.
_Buffer-Deferred
INT64
Total number of changes to blocks that occurred before the blocks were written. Each deferred write is potentially an I/O operation saved.
_Buffer-Free
INT64
Number of free buffers
_Buffer-Flushed
INT64
Number of blocks that were not written during the checkpoint and that had to be written all at once at the end of the checkpoint.
_Buffer-Index
INT64
Number of index blocks buffered
_Buffer-LogicRds
INT64
Number of client requests for database block read operations.
_Buffer-LogicWrts
INT64
Number of client requests for database block write operations.
_Buffer-LRUEnabled
LOGICAL
True when all the buffers in the Alternate Buffer Pool (-B2) are consumed and an LRU replacement algorithm is utilized for buffer eviction.
_Buffer-LRUSkips
INT64
Number of times a buffer on the LRU chain was skipped because it was locked or modified.
_Buffer-LRUwrts
INT64
Number of blocks written to free a buffer for a read operation.
_Buffer-Marked
INT64
Number of blocks scheduled to be written before the end of a checkpoint.
_Buffer-Master
INT64
Buffer identifier. Valid values are:
*0 — Primary buffer pool
*1 — Secondary buffer pool
_Buffer-Object
INT64
Number of object blocks
_Buffer-ObjClist
INT64
Object Cluster List Blocks (contains the list of clusters owned by a particular object)
_Buffer-ObjList
INT64
Number of object list blocks
_Buffer-OSRds
INT64
Number of database blocks read from disk
_Buffer-OSWrts
INT64
Number of database block writes to disk
_Buffer-RM
INT64
Number of record blocks buffered
_Buffer-Seq
INT64
Number of sequence blocks
_Buffer-Trans
INT64
Number of transactions committed
_Buffer-Uptime
INTEGER
Number of seconds the database was opened
1 Activity and status of ABL temp-tables is available in this virtual system table. The statistics gathered allow you to monitor the operation and performance of deployed client temp-tables. Specify the range of temp-tables to track with the -ttbasetable and -tttablerangesize startup parameters. Specify temp table indexes with -ttbaseindex and -ttindexrangesize startup parameters. For more information monitoring and debugging temp tables with VSTs, see OpenEdge Development: Debugging and Troubleshooting.